Temperature accelerated dielectric breakdown of PECVD low-k carbon doped silicon dioxide dielectric thin films

The dielectric breakdown strength of carbon doped silicon dioxide thin films with thickness d from 32 nm to 153 nm is determined at 25 degrees C, 50 degrees C, 100 degrees C, 150 degrees C and 200 degrees C, using I-V measurements with metal-insulator-semiconductor (MIS) structures. It is found that the dielectric breakdown strength, E-B, decreases with increasing temperature for a given film thickness. In addition, a film thickness dependence of breakdown is also observed, which is argued to show an inverse relation to thickness d in the form of E-B proportional to (d-d(c))(-n). The exponential parameter n and critical thickness limit d(c) also exhibit temperature dependent behavior, suggesting a temperature accelerated electron trapping process. The activation energy for the temperature acceleration was shown to be thickness dependent, indicating a thickness dependent conduction mechanism. It is thereafter demonstrated that for relatively thick films (thickness > 50 nm), the conduction mechanism is Schottky emission. For relatively thin films (thickness < 50 nm), the Schottky conduction mechanism was obeyed at low field region while FN tunnelling was observed as a prevail one in the high field region.